Apparatus and system for inspecting wall thickness of synthetic resin containers

ABSTRACT

This invention relates to an inspection system for a container made of synthetic resin, comprising: a wall thickness inspecting apparatus having a projector for emitting an inspection light guided from a light source inserted into a container made of synthetic resin and provided with one end opened towards the wall of the container, a light receiver arranged in opposition to the projector at an external portion of the container for receiving the inspection light passing through the wall of the container and converting the received light into an electric signal, and an arithmetic operation device for calculating the wall thickness of the container on the basis of the output signal from the light receiver; a first container conveying station provided with a plurality of container holders arranged around the circumference of a rotary disc with predetermined spaces; a container feeding station for feeding the containers to a container conveying passage of the first container conveying station with the interval equal to that between the adjacent holders; a first inspecting station for inspecting the existence of the heat resistant resin of the container; a second inspecting station for inspecting the wall thickness of the container; a second container conveying station provided with a container receiving end portion for receiving the container determined to be a good product by the inspections of the first and second inspecting stations and conveying the container externally of the first container conveying station.

TECHNICAL FIELD

This invention relates to an apparatus and system for inspecting a wallthickness of a container of a cylindrical bottomed structure made ofsynthetic resin and adapted to be filled with any kind of drink such assoft drink, juice or like drink (called merely drink hereinafter).

PRIOR ART

Recently, soft drinks have been sold in a state of being filled in acontainer having a large volume and, generally, the container of thistype is made of a polyethylene terephthalate resin (PET resin). Thedrink is heated to a relatively high temperature of about 85° when thedrink is filled into the container, so that an opening portion and ashell portion of the container may be deformed by the heated drink uponthe filling thereof. Moreover, when the container filled with the heateddrink is closed with a lid and, thereafter, cooled, an inner pressure inthe container is lowered, so that the shell of the container may bedeformed inwardly. Such adverse phenomenon will be caused when acontainer having a shell with a long longitudinal length is utilized. Inorder to obviate this adverse phenomenon, there has been proposed acontainer having the shell provided with a column like portion extendingin the axial direction of the container and having a corrugated sectionto strengthen the structure of the shell of the container. However, theprovision of such container does not necessarily adequately obviate thedefects described above.

In another aspect, in order to obviate the defects, the opening portionof the container is crystallized to provide a heat resisting property oris formed of a heat resistant resin. However, in the latter mentionedmethod, there is a problem in that it becomes impossible to inspect thewall thickness of the container in a case where the PET resin and theheat resistant resin have the same color or are both transparent. In themeantime, regarding the shell of the container, a destructive inspectionbased on a sampling method can be utilized for the inspection ofproducts, but this inspection involves unstable requirements for themanufacture of the container and, particularly, in a case where there isa fear of an unforeseen occurrence of a faulty product, it is absolutelynecessary to carry out 100% inspection of the containers.

Taking the above matters into consideration, the applicant of thisapplication has proposed an inspection method and device, for theopening of the container, for measuring an amount of a heat resistantresin by utilizing the nature of the PET resin which has thepermeability, or allows the transmission of ultraviolet rays withspecific wavelengths larger than that of the heat resistant resin(Japanese Patent Application No. 61-289864). The applicant has furtherproposed a container rotating mechanism for improving the inspectionaccuracy by holding the container securely and smoothly rotating thesame (Japanese Patent Application No. 62-7743). According to the methodand device proposed above, it becomes possible to incorporate a processfor inspecting the heat resistance of the opening portion of thecontainer into a continuous automatic container manufacturing line. Itbecomes also possible to measure, at the same time, the degree oftransparency, verticality, height, amount of bubbles in the openingportion and air tightness of the container.

With the inspection to the heat resistance of the container, theinspection of the opening portion can be sufficiently made by measuringthe amount of the heat resistant resin of the opening, whereas it isabsolutely necessary for the inspection of the shell portion to measurethe wall thickness of the shell because it is required for the containerto have some degree of thickness to keep the good heat resistingproperty of the shell of the container.

The measurement of the wall thickness of the container is performed bydirect destructive means in which the shell of the container is cut andthe thickness thereof is measured, or by non-contact or non-destructivemeans in which many kinds of rays or beams or ultrasonic waves areutilized. However, the containers have been manufactured in accordancewith an automatic continuous manufacturing line, so that the utilizationof a noncontact or non-destructive method is desirable for theinspection method.

DISCLOSURE OF THE INVENTION

A primary object of this invention is to provide an apparatus forinspecting a wall thickness of a container made of synthetic resin, andwhich is capable of inspecting with good precision the thickness by anoncontact method or a non-destructive method.

A secondary object of this invention is to provide an inspection systemcapable of effectively carrying out the inspection regarding the heatresistance of the container in an automatic continuous manufacturingline for containers made of synthetic resin and capable of improving themanufacturing efficiency of the containers and maintaining the stablequality of the containers.

(1) The first characteristic feature of this invention resides in theprovision of an apparatus for inspecting a wall thickness of a containermade of synthetic resin, the apparatus comprising a projector forprojecting an inspection light, towards a wall surface of a containermade of synthetic resin, emitted from a light source inserted into thecontainer through an opening formed at one end thereof, a light receiverarranged externally on the container at a portion opposed to theprojector and adapted to receive the inspection light passing throughthe container wall and convert the thus received light into an electricsignal, and an arithmetic operating means for calculating the wallthickness of the container from the output signal from the lightreceiver.

(2) The second characteristic feature of this invention resides in theprovision of an inspection system for a container made of syntheticresin, the inspection system comprising, in the described order, thefirst container conveying station in which a plurality of containerholders are arranged at predetermined distances around thecircumferential direction of a rotary disc, a container feeding stationdisposed above a circular container conveying passage of the firstcontainer conveying station and adapted to feed the containers to thefirst container conveying station at intervals equal to the distancebetween the respectively adjacent container holders, the firstinspection station for inspecting the existence of a heat resistantresin at the opening portion of the container, the second inspectionstation for inspecting a wall thickness of the container, the secondcontainer conveying station provided with a container receiving portionfor conveying the containers which are inspected and judged as productswith no faults at the first and second inspection stations, and thefirst container discharging station for discharging the containersjudged to have a fault at at least one of the first and secondinspection stations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general view of the first embodiment of an apparatus,according to this invention, for inspecting a wall thickness of acontainer made of synthetic resin;

FIG. 2 is a front view showing a mechanical structure of the apparatusshown in FIG. 1;

FIG. 3 is a side view showing a mechanical structure of the apparatusshown in FIG. 1;

FIG. 4 is a perspective view showing the standing condition of thecontainer and the arrangement of a projector and a light receiver in theinspection apparatus shown in FIG. 1;

FIG. 5 is a circuit diagram for the inspection apparatus shown in FIG.1;

FIG. 6a, 6b, 6c, 6d, 6e, and 6f show time charts of output signals to betransmitted from the respective portions of the inspection apparatusshown in FIG. 1;

FIG. 7 shows a graph representing the relationship between the wallthickness of the container and the output voltage of a photoelectrictransfer element;

FIG. 8 is an illustration of the general arrangement of the secondembodiment of an apparatus, according to this invention, for inspectingthe wall thickness of a container made of synthetic resin;

FIG. 9 is a brief side view of an insertion tube and a controller forthe elevation of the insertion tube used for the apparatus shown in FIG.8;

FIG. 10 is a sectional view of a light receiving sensor of theinspection apparatus shown in FIG. 8;

FIG. 11 is a side view partially in section of a light emitting sourceand a light illuminating portion of the inspection apparatus shown inFIG. 8;

FIG. 12 is a diagram showing a synthetic resin container manufacturingsystem provided with the thickness inspection apparatus shown in FIG. 8;

FIG. 13 is a diagram showing a synthetic resin container manufacturingsystem of conventional type;

FIG. 14 is a plan view of a container rotating and conveying unit towhich the inspection apparatus shown in FIG. 8 is arranged;

FIG. 15 is a flowchart for performing the processes of the inspectionapparatus shown in FIG. 8;

FIG. 16 shows a modification of the inspection apparatus shown in FIG.8;

FIG. 17 is a plan view of an inspection system, according to thisinvention, for a container made of synthetic resin;

FIG. 18 is a plan view of the first container conveying station of theinspection system shown in FIG. 17;

FIG. 19 is a side view of the inspection system shown in FIG. 17; and

FIG. 20 is a side view, partially in section, of the second inspectionstation of the inspection system shown in FIG. 17.

BEST MODES FOR EMBODYING THE INVENTION 1 First Embodiment of WallThickness Inspection Apparatus for a Synthetic Resin Container 1--1Basic Structure

General Structure

FIG. 1 shows the general structure of the first embodiment of anapparatus, according to this invention, for inspecting a wall thicknessof a container made of synthetic resin. Referring to FIG. 1, thethickness inspection apparatus comprises a light projector 104 insertedinto a container 101, for example, preferably a bottle, through anopening 102 thereof and adapted to emit an inspection light 103 towardsa shell wall of the container 101, a light receiver 105 arrangedexternally of the container 101 so as to oppose a light projectingportion of the projector 104 with the shell wall portion interposedtherebetween with a predetermined space, an arithmetic operation unit106 for calculating the wall thickness of the inspected portion of thecontainer 101 in response to an output signal from the light receiver105, an elevating means 108 for elevating the projector 104 and thereceiver 105 together, and a rotating means 109 for rotating thecontainer 101 in the circumferential direction of the container 101 atan inspecting portion. According to the construction of the inspectionapparatus described, the elevating means 108 and the rotating means 109constitutes an inspecting position changing unit, in which the rotatingmeans is a circumferential inspecting position changing means for thecontainer 101.

Container 101

The container, an object to be inspected, 101 is made of a syntheticresin material prepared by mixing a resin having a heat resistingproperty such as polyallylate resin with a PET resin. The container isthus transparent or translucent. The container 101 is formed by aninjection molding method in which both the resins described aresimultaneously injected into a mold. As described hereinbefore, theopening portion of the container 101 is formed by concentrating thepolyallylate resin to maintain the heat resisting property at thatportion. The shell wall portion of the container has a laminatedstructure in the thickness direction formed, as a three-layeredstructure, by inner and outer layers of PET resin and a layer of theheat resistant resin interposed between the PET resin layers.

Projector 104

As shown in FIG. 1, the projector 104 generally comprises a lightemitting portion 110 and a light guiding portion 111.

The light emitter 110 is accommodated in a casing 112 and comprises alight source 113, a concave mirror arranged above the light source 113,a chopper 115 disposed below the same, and a pin hole 116 formed in thebottom portion of the casing 112.

The light source 113 is composed of a material, such as a nichrome wire,emitting an infrared ray as an inspection light. It is preferred toutilize infrared rays having a wavelength of 2 to 5 μm for the reasonthat if the infrared rays have a longer wavelength, it is necessary toelongate a light passage constituted by a lens unit and this results inthe elongation of the light guide 111. As this is not practical, and ifthe infrared ray having a long wavelength of, for example, 15 to 18 μmis utilized, and it is necessary to utilize a blackbody furnace. Theusage of the blackbody furnace makes the whole apparatus expensive.

The concave mirror 114 is located so as to concentrate the infrared raysemitted from the light source 113 and has a focal point on the pin hole116.

The chopper 115 is arranged so as to chop the light reflected by theconcave mirror 114 and towards the pin hole 116 to obtain light having adiscontinuous shape, i.e. alternating wave shape. The reason forcarrying out the chopping operation is based on the fact that it isnecessary to eliminate variable factors such as drift and offset on thebasis of the characteristics of the photoelectric transfer elementprovided for the light receiver 105 described hereinlater for the highprecision inspection of the container and, hence, it is necessary tochange the shape of the light once so as to have the alternating waveshape to deny the drift and offset and then to transfer into the D.C.shape. Such chopping operation may be performed by an electric means inwhich electric signals applied to the light source 113 are chopped, orby a mechanical means as in this embodiment in which the light emissionfrom the light source is made constant, but the light therefrom isintermittently shut out by a chopper plate 117 which is rotated by anelectric motor 118 with a predetermined speed of revolution.

The light guide 111 extends downwardly from the bottom of the casing 112at a portion corresponding to the location of the pin hole 116. Theinspection light 103 reflected by the concave mirror 114 and convertedinto the alternating wave shape by the chopper 115 is guided into thelight guide 111 through the pin hole 116. A lens system 119 consistingof a plurality of lens units arranged in multistage series is arrangedin the light guide 111. The inspection light 103 through the pin hole116 is made into parallel light beams through the final stage lens unit120 and the parallel light beams are then reflected by a reflectingmirror 121 arranged at the front end portion of the light guide 111 withan inclination of 45° with respect to the projected light. The reflectedlight projects as a spot light 103 towards the shell wall of thecontainer in the form of a bottle 101.

Light Receiver 105

As shown in FIGS. 1, 2 and 3, the light receiver 105 is attached to thecasing 112 by a supporting member at a position opposing the lightprojecting end portion of the light guide 111, i.e. the reflectingmirror 121 with a predetermined interval in the light reflectingdirection. The light projector 104 and the light receiver 105 are alwaysintegrally held with a constant relative relationship maintainedtherebetween.

The light receiver 105 comprises a casing 122 provided with a lightreceiving window 122a, an interference filter 124 provided for thewindow 122a and a photoelectric transfer element 123 disposed behind theinterference filter 124. The interference filter 124 has the charactthecharacteristics to filter the specific wavelength (2.6 μm) as a peak soas to accord with the spectral characteristics relative to the thicknessof the container 101 and to shut out unnecessary wavelengths of theexternal disturbance noise. The photoelectric transfer element 123 isusable at a usual temperature or a constant temperature and it isdesired that the spectral characteristics are made to peak at thewavelength of 2 to 5 μm in accordance with the inspection light 103 forimproving the SN (signal-to-noise) ratio. A PbS (lead sulfide)photoelectric transfer element may be utilized for this purpose.

Electric Signal Processing Unit

The electric signal processing unit utilized for the apparatus accordingto this embodiment comprises, as shown in FIG. 1, a chopper circuit 126for driving the chopper 115, a signal processing circuit 127 forconverting the output signal from the photoelectric transfer elementinto a D.C. wave shape (peak hold wave shape) with a chopper outputsignal A as a timing signal, an arithmetic operating circuit 128 forcalculating a wall thickness of a container shell portion to beinspected on the basis of the output signal processed by the processingcircuit 127, a rotary encoder 131 for detecting the rotating position ofthe rotating means 109, described hereinafter, i.e. a circumferentialposition of the container 101, a potentiometer 132 for detecting thepositions of the projecting portion of the projector 104 and the lightreceiving portion 105 in the axial direction of the container 101, and adisplay unit 129 for displaying the thickness distribution of thecontainer 101 in the circumferential direction thereof on the basis ofthe operated output signal (wall thickness t) and the output signal fromthe encoder 131 and displaying the thickness distribution of thecontainer 101 in the axial direction thereof on the basis of theoperated output signal (wall thickness t) and the output signal from thepotentiometer 132.

The chopper circuit 126 serves to output the inspection light of thealternating shape form by rotating the D.C. motor 118 at thepredetermined speed of revolution and then rotating the chopper plate117 provided with cutouts, not shown, formed intermittently along thecircumferential direction thereof. The chopper circuit 126 transmits thetiming signal A corresponding to the chopping period of the inspectionlight 103 (FIG. 6(a)). The timing signal A is then input into the signalprocessing circuit 127.

The signal processing circuit 127 comprises, as shown in FIG. 5, aprimary delay circuit (integrating circuit) 146 for outputting a timingsignal A₁ generated by delaying the timing signal A by the predeterminedtime constant, a secondary delay circuit (integrating circuit) 147 foroutputting a timing signal A₂ generated by further delaying the timingsignal A₁, an edge detecting circuit (differentiating circuit) 134 fordetecting the transition edge of the thus twice delayed timing signalA₂, a duration circuit 135 for converting the edge signal transmittedfrom the edge detecting circuit 134 into a signal voltage of TTL level,and a peak hold circuit 136 for peak holding the output signal from thephotoelectric transfer element 123 with the converted signal being as areset input signal R. It is to be noted that the delay circuit means isnot necessarily constituted by the two staged delay circuits asdescribed above and only one delay circuit may be utilized in a casewhere the single staged delay circuit ensures the delay time constantrequired.

The primary and secondary delay circuits 146 and 147 are active circuitsutilizing CR integrating circuits and operation amplifiers and serve todelay the output signals A from the chopper circuit into the outputsignals A₁ and A₂ having phases represented by FIGS. 6(b) and 6(c). Thetime constant τ is adjustable by rendering variable the resistance R inthe CR integrating circuit.

The edge detecting circuit 134 is a differentiating circuit including acapacitor C_(O) and serves to detect the transition edge of the timingsignal A₂ and then to transmit an output signal A₃ from the edgedetecting circuit 134 having an actual output of differential wave shape(FIG. 6(d)).

The duration circuit 135 serves to output the reset signal R at the TTLlevel (logical signal level: 5V) to be in accordance with the signallevel of the peak hold circuit 136 and an open collector circuit isutilized as a circuit element. The reset signal R is transmitted to theinput end terminal of the peak hold circuit 136.

The peak hold circuit 136 includes a ground holding capacitor C_(H) tohold the peak level of an output signal B to the next peak and to outputa value corresponding to the wall thickness of a portion to be inspectedof the container 101. This means the equivalency of the conversion intoD.C. signal only in view of the peak of the alternating signal in thechopper period. Reference numeral 133 designates a bypass filter foreliminating the drift of low frequency contained in the output signal Bfrom the photoelectric transfer element 123.

The arithmetic operation circuit 128 serves to calculate the shell wallthickness t of the container 101 from the relative relationship betweenthe output obtained from the photoelectric transfer element 123 (i.e.transmitting amount of the inspection light through the shell wall ofthe container 101) and the thickness t of the container 101. FIG. 7represents a graph showing the relationship described above, in whichthe output voltage V is divided by the initial output voltage V_(O) tobecome dimensionless in view of the initial output voltage inclusive ofvariable of the photoelectric transfer element 123. In the experimentalexample, the output voltage V* made to be dimensionless is expressed asfollows.

    V*=83×exp(-1.367t)

This equation is modified as follows.

    t=ln(83/V*)/1.367                                          (1)

where V*=V/V_(O) ×100; V: actual output voltage; and V_(O) : initialoutput voltage. Accordingly, the wall thickness t can be immediatelycalculated when the voltage V of the output signal B of thephotoelectric transfer circuit 123 is obtained. Such arithmeticoperation circuit 128 may be realized by utilizing a logarithmicamplifier set to a constant satisfying the above equation (1) or acalculating element such as a personal computer.

The display unit 129 may utilize an X-Y recorder, for example. When itis required to display the distribution of the wall thickness of thecontainer in the circumferential direction thereof, the encoder 131outputs a signal E regarding the circumferential directional measuringposition into the X-axis input terminal and an output signal D(thickness t) from the arithmetic operation circuit 128 into the Y-axisinput terminal, to thereby confirm the matching of the display to thestandard specification. In case of the display of the distribution ofthe axial thickness of the container 101, the display may be obtained byinputting a signal F regarding the axial measurement position from thepotentiometer 132 into the X-axis input terminal and inputting an outputsignal D from the arithmetic operation circuit 128 into the Y-axis inputterminal.

Elevating Mechanism 108

The elevating mechanism 108, as shown in FIG. 2 or 3, comprises anelectric motor 137 secured to the casing 112, an elevation guide 139mounted on a supporting column 138, an elevation guide rod 140 forprecisely performing the elevating motion, and a supporting member 141for supporting the elevation guide rod 140. A rack, not shown, isdisposed to a portion of the casing 112 corresponding to the location ofthe elevation guide 139 and a pinion, not shown, which is meshed withthe rack is disposed on the side of a slider 142. According to thisconstruction, when the pinion is rotated by the motor 137, the casing112 is moved in the vertical direction. Reference numeral 143 designatesa lock lever for locking and holding the light projecting portion of thelight guide 111 of the projector 104 at an optional position. The motionof the elevation guide rod 140 is restricted by clamping the lock lever143. Accordingly, the light guide 111 and the light receiver 105 securedto the casing 112 are both elevated together with the guide rod 140, sothat the axial inspection of the container can be thus made.

Rotating Mechanism 109

The rotating mechanism 109, as shown in FIGS. 2 and 3, comprises aturntable 144 on which the container 101 can be held in a standingcondition and a change gear 145 for changing the rotation speed of theturntable 144 so as to be rotated with proper revolution numbers andtransmitting the changed revolution numbers. The turntable 144 isindependently rotated without being synchronized with the chopper outputsignal A. For this reason, the encoder 131 is located for making clearthe circumferential position of the container. The circumferentialinspection of the container 101 can thus be made possible. Theindependent rotation of the turntable 144 is made in consideration ofthe optional change of the rotation of the container 101.

1-2 Inspecting Operation due to Basic Structure

A series of inspecting operations is performed in the following manner.

A container 101 as an object to be inspected is first mounted on theturntable 144 (FIG. 4). The elevation mechanism 108 is then operated tolower the casing 112 together with the light guide 111 so as to insertthe light guide 111 into the container 101 through the opening 102thereof (FIG. 4). Upon the stoppage of the turntable 144 at apredetermined inspecting position, the inspection light 103 is emittedfrom the light emitting portion 110 and the inspection light 103 ischopped during this time. The inspection light 103 is guided in thelight guide 111 through the lens arrangement 119, reflected by thereflecting mirror 121 and then projected outwardly from the interior ofthe container 101 through the shell wall thereof. The inspection light103 through the shell wall is received by the photoelectric transferelement 123 of the light receiver 105, from which an output signal Bhaving a magnitude corresponding to the transmitting light amount istransmitted (FIG. 5 and FIG. 6(f)). The output signal B from thephotoelectric transfer element 123 is then transmitted into the signalprocessing circuit 127 and the chopper output signal A is also inputinto the signal processing circuit 127.

The signal processing circuit 127 serves to delay the phase of thechopper circuit output signal A in two stages by the delay circuits 146and 147 (FIG. 6(c)) for the purpose of the synchronism for sampling thepeak value by means of the peak hold circuit 136 (FIG. 6(e)). Thisdelayed phase τ is detected by the edge detection circuit 134 and thereset signal R (i.e. edge detection circuit output signal A₃, FIG. 6(c))is transmitted to the peak hold circuit 136. Accordingly, when the resetsignal R is input, the peak hold circuit 136 serves to reset the peakvalue held at this time and to perform the sampling of a new peak valueFIG. 6(e). A value C in this sampling corresponds to the wall thicknesst of the container 101. The sampling value C is then transmitted to thearithmetic operation circuit 128, which outputs the signal Dcorresponding to the wall thickness t in accordance with the equation(1) described before.

During this period, the signal E representing the rotating position ofthe turntable 144 (i.e. circumferential position of the container 101)is input into the display unit 129, into which the signal D representingthe wall thickness calculation is also input, whereby the thicknessdistribution in the same direction is displayed on the display unit 129.

In the meantime, when the rotation of the turntable 144 stops and thelight guide 111 is elevated, the signal F representing the inspectionposition in the axial direction of the container is transmitted from thepotentiometer 132 into the display unit 129 and the wall thicknesscalculation signals D corresponding to the respective inspectionposition signals F are recorded, whereby the thickness distribution inthe axial direction can be obtained.

1-3 Effects

According to the first embodiment described hereinbefore, the followingeffects will be attained.

(1) A wall thickness of a container can be precisely inspected by anon-contact and non-destructive method. Accordingly, a container havinga constant wall thickness can be manufactured, whereby the quality ofthe manufactured container can be improved.

(2) The thickness inspection can be performed with respect to everyportion including the circumferential direction or the axial directionof the container such as bottle by an inspection position changingmeans, whereby the 100% inspection of the bottle can be performed anddetailed analysis data regarding the wall thickness of the bottle can beobtained.

2 Second Embodiment of Wall Thickness Inspection Apparatus for SyntheticResin-made Container 2-1 Basic Structure

The second embodiment of an inspection apparatus, according to thisinvention, for inspecting a wall thickness of a container made ofsynthetic resin will be described hereunder with reference to FIGS. 8 to16.

The inspection apparatus 201 of the second embodiment comprises, asshown in FIG. 8, an arithmetic control operation unit 202 for performingthe control of the entire apparatus and arithmetic processing of thedata and an inspection unit 203 for inspecting the wall thickness of acontainer.

The control-operation unit 202 comprises a main controller 204 formanaging the control of the whole apparatus, an interface controller (IFcontroller) 205 for controlling the giving and taking of the databetween the inspection unit 203, etc., a chopper driver 206 for drivingthe chopper, a signal processor 207 for converting output signals formthe chopper and the light receiver, described later, into D.C. waveshapes, a rotary encoder 208 for detecting the position of rotation of adevice 250, described later, for continuously and automatically rotatingand conveying the container, and an arithmetic operation processor 209for performing the operation processing of the data.

The chopper driver 206 serves to rotate a chopper plate 211 at aconstant speed at revolution under the control of the revolution numberof the motor with a rotation control signal 215 and to output a timingsignal 212 corresponding to the chopping period into the signalprocessor 207.

The signal processor 207 serves to convert an output signal 214, basedon the timing signal 212, from a light receiving element 213 into a D.C.wave shape (peak hold wave shape) and to transmit the thus obtained waveshape into the main controller 204 through the IF controller 205.

The rotary encoder 208 serves to detect the position of rotation of thecontainer rotating and conveying device 250, to convert the thusdetected value into an electric signal and to output the signal into themain controller 204 through the IF controller 205.

The inspection unit 203 comprises a light projector 290 provided with aninsertion tube 217 to be inserted into a container 216 made of syntheticresin, a controller 218 for controlling the elevation of the insertiontube 217 into and out of the container 216, a light emitting source 219for emitting an inspection infrared ray 219, a light emitter 220 foremitting the inspection infrared ray to the insertion tube 217, and alight receiver 213 for converting the infrared ray from the insertiontube through the shell wall of the container 216 into an electric signalhaving a magnitude corresponding to the amount of the infrared rayreceived by the light receiver 213.

FIG. 9 shows a general view of the light projector 290 provided with theinsertion tube 217 and the insertion tube elevation controller 218, inwhich the insertion tube 217 is illustrated partially in section for thepurpose of explanation.

Referring to FIG. 9, the insertion tube 217 has a cylindricalconfiguration having upper and lower end portions and openings OU and OLare formed on the side portions of both the end portions of theinsertion tube 217. Reflecting mirrors 350 are disposed inside theopenings. The inspection infrared ray 221 guided into the insertion tube217 through the opening OU, for example, is reflected by the reflectingmirrors 350 and projected towards the shell wall of the containerthrough the opening OL as shown by a dotted line.

In a modification, a lens system may be arranged in the insertion tube217 as occasion demands, and prisms may be substituted for thereflecting mirrors 350.

The insertion tube elevation controller 218 comprises a main frame 351,a pneumatic, i.e. air, cylinder assembly 352 for vertically moving theinsertion tube 217, an insertion tube holder 352 for securing theinsertion tube 217, a guide rod for guiding the pneumatic cylinderassembly 352, adjusters 355a and 355b for adjusting the vertical stoplimit positions of the insertion tube 217, shock absorbers 356a and 356bfor absorbing the shocks at the insertion tube movement stop time, andreturn spring securing pins P and P.

FIG. 10 shows a general view of the light receiver 213.

Referring to FIG. 10, the light receiver comprises an outer casing 222,an interference filter 223 for cutting out a frequency area except forthe specific frequency area of an infrared ray, PbS photoelectrictransfer element 224 for converting the infrared ray into an electricsignal having a magnitude corresponding to the amount of the projectedinfrared ray, an electronic cooling element 225 accommodated in thephotoelectric transfer element 224 for maintaining an inner temperatureof the element 224, an amplifier 226 for amplifying the output signalfrom the photoelectric transfer element 224, a power source connector227 for supplying electric power to the photoelectric transfer element224 and the amplifier 226, an output connector 228 for transmitting anoutput signal 214 amplified by the amplifier 226, and a coolingcontrolling connector 229 for controlling the electronic cooling element225.

The interference filter 223 is provided with a central transmissionwavelength of about 2.6 μm and the infrared ray transmitting theinterference filter 223 is converted into an electric signal by thephotoelectric transfer element 224, then amplified by the amplifier 226and output into the main controller 204 through the IF controller 205.

During these operations, in order to stably operate the PbSphotoelectric transfer element 224, the temperature near thephotoelectric transfer element 224 is maintained to a value of about 10°C. by the electronic cooling element 225 by utilizing the Peltiereffect.

FIG. 11 shows a general view of the light emitting portion 219, thelight emitter 220 and a constant temperature oven 344.

Referring to FIG. 11, the light emitting portion 219 comprises an outercasing 230, a lighting source made of a filament 231, a concave mirror232 disposed above the lighting source 231, a chopper 233 located belowthe lighting source 231, and a circulation fan f attached to a sideplate of the casing 230. The light emitter 220 is disposed below thelight emitting portion 219. As the lighting source 231 is utilized asubstance such as nichrome wire for emitting infrared rays. It isdesired to utilize infrared rays having a wavelength of about 2 to 5 μm.

The concave mirror 232 is located for concentrating the infrared raysfrom the lighting source 231.

The chopper 233 comprises a chopper plate 211 and an electric motor 210for rotation, and serves to chop the infrared ray concentrated by theconcave mirror 232 to obtain interrupted light (alternating wave shape).This chopping operation is performed for the reason such that the driftand offset caused as variable factors due to the characteristic featureof the PbS pohotoelectric transfer element are to be eliminated byconverting the infrared rays into the alternating wave shape to therebyperform precise measurement. Choppers with an electrical structure inwhich the light source, i.e. infrared ray, is electrically chopped maybe utilized as well as those of mechanical structure of the typedescribed with reference to this embodiment.

The light emitter 220 comprises the reflector 235 and the lens system236 and serves to introduce the infrared rays from the lighting source231 into the insertion tube 217 as parallel beams.

Plate-like heat generating members 234 are disposed on all or some ofsurfaces of the constant temperature oven 344 to maintain thetemperature of the interior of the oven 344 at about 40° C. The airhaving the constant temperature in the constant temperature oven isintroduced into the casing 230 of the light source portion 219 by meansof the circulation fan f to maintain the temperature constant in thecasing 230 so as to stably performing the measurement by eliminatingfluctuations of the lighting source 231.

FIG. 12 is a block diagram representing a system for manufacturingcontainers made of synthetic resin in which the thickness inspectingapparatus according to this invention is incorporated.

The system M for manufacturing a container made of synthetic resincomprises a material feeding device 237 for feeding a synthetic resinmaterial, a molding unit 238 comprising an injection molding machine anda blow-forming machine, a controlling unit 239 for controlling themolding or forming condition of the molding unit 238, an inspectingdevice 240 for inspecting the height, for example, of a molded container216, a thickness inspecting device 201 for inspecting the wall thicknessof the container 216, a conveying and rotating device 250 forautomatically and continuously conveying the container 216 to aninspecting position and rotating the same at an inspection time, and adevice 242 for selecting faulty containers and good containers.

FIG. 13 also shows a block diagram representing a conventionalinspection system for containers made of synthetic resin and thisdiagram is employed for comparison with that of FIG. 12.

Referring to FIG. 13, a container manufacturing system m comprises afeeding device 237 for feeding a synthetic resin material, a moldingunit 238 including an injection molding machine and a blow formingmachine, a controlling unit 239 for controlling the molding and formingcondition of the molding unit, an inspection device 240 for inspectingthe molded container 216, and a device 242 for selecting the faultyproducts and the good products in accordance with the inspection. Athickness inspecting device 330 may be further provided as occasiondemands, for the system for inspecting the wall thickness of thecontainer by a manual sampling method.

The difference between the systems shown in FIG. 12 and FIG. 13 residesin that the system according to the embodiment of this inventionincludes the inlined type of wall thickness inspection device 201 andthe container conveying and rotating device 250 arranged between theinspection device 240 and the selecting device 242. According to theprovision of these further devices, the thicknesses of the containerscan be continuously and automatically inspected immediately after themolding process and the data so obtained can be fed back so as topromptly implement a necessary procedure for the molding process.

Referring to FIG. 12, the material feeding device 237 feeds as a mainresin material a polyethylene terephthalate type synthetic resin to themolding unit 238.

The molding unit 238 includes the injection molding machine and the blowforming machine. The injection molding machine is operated for preparinga parison for the blow formation with the resin fed from the materialfeeding device 237 and the parison transferred to the blow formingmachine is subjected to the expansion blow formation so as to have ashape of a container. The molding conditions of the molding unit arecontrolled by the controlling unit 239.

The container of synthetic resin thus molded by the molding unit 238 isthen conveyed to the inspection device 240.

FIG. 14 is a detailed view of the continuously conveying and rotatingdevice 250.

Referring to FIG. 14, the conveying and rotating device 250 comprises aturntable 251, four holders 252 mounted on the turntable 251 for holdingand releasing the containers, the holders being arranged with an angularspace of 90° with respect to each other, pressing members 253 forreleasing the holding condition of the holders by applying pressurethereto at the container feeding and discharging times, and a cylinderassembly 254 for operating the pressing members 253.

Container take-in and take-out conveyers 255 and 256 are furtherconnected to the turntable 251 so as to extend across the diameter ofthe turntable.

Each of the holder 252 includes a pair of holding members 315, eachhaving three arm portions, for holding and releasing the container 216.The holding member 315 comprises clamp arms 257, arms 258 for openingand closing the clamp arms in association with the pressing member 253,and return arm 259 to which return springs 262 are connected to apply anurging force to close the clamp arms 257. The return arms 259 abutagainst return position adjusting screws 263 at the returning thereof. Aroller 260 for rotating the container at the time of inspection isdisposed between the paired holding members 315 and follower rollers 261are secured to the front ends of the clamp arms 257 to rotate thecontainer in operative association with the roller 260.

2--2 Inspection Operation of the Basic Structure

The operation of the thickness inspection device will be describedhereunder with reference to the flow chart shown in FIG. 15.

Preoperation for Inspection

The light source 231 and light receiving device 213 are preliminarilytest operated for ensuring stable measurement.

(Step 1)

Take-in Conveying of Container

The container 216 is conveyed into an introduced position 291 by theconveyer 255 and when the introduction of the container is detected by aposition detecting sensor, not shown, (Step 2), the pressing member 253is operated by the actuation of the cylinder assembly 254 to press thearms 258 of the holding member 315 positioned at the containerintroduction position 291 for a thickness inspection unit operated in acontinuous and automatic manner, whereby the clamp arms 257 are openedwidely about pins 310 against the urging force of the return springs 262and the return arms 259 are separated from the return positionadjustment screws 263.

The container 216 is conveyed into the paired holding members 315 by theconveyer 255 with the clamp arms 257 being opened. When it is detectedby a position detecting sensor, not shown, that the container 216 isconveyed to a position at which the container 216 contacts the rotationroller 260, the pressing force to the pressing member 315 is releasedand the return arms 259 abut against the returning position adjustingscrews 263 by the urging force of the return springs 262, whereby thecontainer 216 can be surely held by the holding members 315 by thecooperation of the roller 260 and the following rollers 261 (Step 3).

The turntable 251 is next rotated in a clockwise direction on thedrawing paper and stops at a position in which the container 216 isconveyed to an inspection position 292 while maintaining the conditionheld by the holding members 315 (Step 4).

Thickness Inspection

The roller 260 is rotated and the container 216 and two follower rollers261 are also rotated in association with the rotation of the roller 260(Step 5). At the same time, the pneumatic cylinder 352 of the insertiontube elevation control unit 218 is operated to be lowered along theguide rod 354 against the urging force of the rerturn springs and theinsertion tube 217 secured to the securing portion 353 also lowers intothe container 216. The insertion tube 217 lowers in the container 216 bythe time when the shock absorbing member (vibration preventing rubber)356a abuts against the lowering motion stopping position adjustingmember 355a. When the shock absorbing member 365a abuts against thestopping position adjusting member 355a, the pneumatic cylinder is heldat that position. The vibration caused by this abuttment can be promptlyabsorbed by the shock absorbing member 365a to promptly keep the stablecondition of the container 216 (Step 6). When the fact that therevolution number of the container 216 reaches the constant value isconfirmed by the output signal from the rotary encoder 208, the maincontroller 204 generates instructions to commence the thicknessinspection (Step 7).

The infrared rays (wavelengths of 2 to 5 μm) emitted from the lightemitter 214 passes the interior of the insertion tube 217 and areprojected on the container 216 through the reflecting mirror 350. Thereflected light then reaches to the light receiver 213 with a partabsorbed by the shell wall of the container 216 and the received lightis converted into an electric signal in the light receiver 213, which isthen transmitted to the signal processing unit 207. The signalprocessing unit 207 serves to convert the signal from the light receiver213 into the D.C. wave shape (peak hold wave shape) on the basis of thetiming signal 212 corresponding to the chopping period of the chopperdriving device 206 and the converted wave shape is transmitted into themain controller 204 through the IF controller 205 (Step 8).

At the same operation time, the rotary encoder 208 detects the rotatingposition of the container rotating and conveying device 250 and thedetected rotating position is converted into an electric signal which isthen transmitted into the main controller 204 through the IF controller205.

Arithmetic Operation Processing

The main controller 204 transfers the output signal data to thearithmetic operation unit 209 so as to convert the output signal datainto data regarding the wall thickness of the container. The arithmeticoperation unit 209 operates to convert the output signal datacorresponding to the amount of the measured infrared ray as shown inFIG. 7 and output the thus converted data into the main controller 204(Step 9). The main controller 204 transfers the data of the wallthickness to the controller 239 for the molding unit 238 through the IFcontroller 205 (Step 10)

Draw-out of the Insertion Tube

The operation of the pneumatic cylinder 352 is thereafter stopped by theinstructions from the insertion tube elevation controller 218 and thenelevated till the time when the shock absorbing member 356b abutsagainst the upper movement stopping position adjusting member 355b. Theinsertion tube 217 is thus easily drawn out from the container 216 (Step11). At the same time, the rotation of the roller 260 stops and, hence,the rotation of the container 216 also stops (Step 12).

Conveying-out of the PET Container

Next, the turntable 251 is again rotated with the container 216 held andstops at the time when the holding members 315 reach the dischargingposition 293 (Step 13). The pressure applying cylinder assembly 254 isthen operated to press the arms 258 of the holding member 315 throughthe pressing member 253, whereby the arms 258 are widely pivotablyopened about the pins 310 against the urging force of the return springs262 and the container 216 is thus released (Step 14). During thisoperation, the return arms 259 are released from the returning positionadjusting screws 263.

The container 216 is then conveyed out of the clamp arms 257 by theconveyer 256 with the clamp arms 257 being opened (Step 15).

When the fact that the container 216 is discharged to the predeterminedposition, is detected by a position detection sensor, not shown, theoperation of the cylinder assembly 254 stops to stop the pressing to thepressing member 253. Then, the pressure of the pressing member 253 isreleased and the return arms 259 abut against the returning positionadjusting screws 263 by the urging force of the return springs 262, thusclosing the clamp arms 257. The turntable 251 is again rotated and thedescribed steps are repeated.

The container 216 is conveyed to the next station for the subsequentoperations by means of the conveyer 242.

Feedback Control

The controller 239 for the molding unit 238 receiving the data regardingthe wall thickness of the container performs control of the moldingcondition in accordance with the data.

2-3 Other Embodiments

The other embodiments will be described hereunder.

A wall thickness inspecting apparatus 279 generally comprises, as shownin FIG. 16, a control operation unit 202 for performing overall controland the operation processing and an inspection unit 280 for carrying outthe thickness inspection.

The control operation unit 202 has a construction substantially the sameas that of the construction described with reference to 2-1 BasicStructure.

The inspection unit 280 comprises a light source 219 for emitting aninfrared ray for the measurement, a guide insertion tube 281 to beinserted into the container for introducing the infrared ray 221 for theinspection, an insertion tube elevation controller 282 for performingthe insertion and the take-out of the insertion tube 281 into and out ofthe container 216, and a light receiver 213 for receiving the lightthrough the shell wall of the container 216 and converting the lighti.e. infrared ray into an electric signal having a magnitudecorresponding to the amount of infrared rays passing through the shellwall.

The guide insertion tube 281 is formed to have a cylindrical shape intowhich flexible fibers 283 adapted for the infrared rays (for example,TlBrTll fluoride glass fibers) are accommodated and one end of the fiberflux is connected to the light source 219. The insertion tube 281 isinserted into the container 216 to be inspected by the insertion tubeelevation controller 282 and the infrared ray 221 generated from thelight source 219 for the inspection is introduced into the container 216through the fibers 283 accommodated in the insertion tube 281.

With the embodiment shown in FIG. 16, the inspecting operation will beperformed by substantially the same processes as described withreference to 2--2 Inspecting Operation.

According to this embodiment, the disturbance which may occur during thelight transfer period will be reduced.

2-4 Effects

According to this embodiment, the following effects can be attained. Thelight projector provided with the insertion tube is constructed to bevertically movable independently, so that the construction of the entirethickness inspecting apparatus for a container made of synthetic resincan be made compact in a case where the apparatus is incorporated in thecontainer manufacturing line and the stable measuring condition can beestablished in a short time.

3 Embodiment of Inspection System for Synthetic Resin-made Container 3-1Basic Structure

An embodiment of an inspection system for a synthetic resin-madecontainer according to this invention will be described hereunder withreference to FIGS. 17 to 20.

FIG. 17 shows a general arrangement of the inspection system for acontainer made of synthetic resin according to this invention and theinspection system includes the first container conveyer 402 providedwith a plurality of container holders arranged around the circumferenceof a rotary disc 403 with equal spaces between the adjacent holders (60°, in the illustrated embodiment). Along the circular container conveyingpassage of the first container conveyer 402 are arranged, in thedescribed order, a container feeding station 405 for feeding containers401, the first inspecting station 407 for inspecting the existence of aheat resistant resin at the opening of the container 401, the secondinspecting station 408 for inspecting the wall thickness of the shell ofthe container, a container receiving portion 409 of the second containerconveyer 411 for receiving the container 401 judged to be a good productthrough the inspections at the first and second inspecting stations 407and 408 and for conveying the good product externally of the system, andthe first container discharging station 410 for discharging, through thesecond container conveyer, a container 401 judged to be a faulty productby at least one of the first and second inspecting stations 407 and 408.The second container conveyer 411 is provided with a container conveyingpassage along which are arranged the third inspecting station 412 forinspecting the air tightness of the container 401 and the secondcontainer discharging station 413 through which a container 401 judgedto be a faulty product by the third inspecting station 412 is dischargedthrough the second container conveyer 411.

The first container conveyer 402 is provided with, as shown in FIGS. 18and 19, a rotary disc 403 which is rotated by a driving device, notshown, together with a rotation shaft secured to the central portion ofthe rotary disc. The container holders 404 are arranged along thecircumferential portion of the rotary disc 403 with equal spaces (sixholders 404a, 404b, 404c, 404d, 404e and 404f, in the illustratedembodiment).

Each of the container holders 404 comprises a driving roller 441 mountedto a shaft 442 and a pair of rotation rollers 443 supported by asupporting rod 444 to be rotatable. Each of the supporting rods 444 issupported by an open-to-close arm 444a to be opened or closed. Therespective three rollers 441, 443 and 443 are positioned at the apexesof a triangle. A rotation gear 445 is arranged on the driving roller 441on the inner peripheral side of the rotary disc 403.

A stationary shaft 446 is mounted on the upper portion of the rotarydisc 403 regardless of the rotation of the rotation shaft and astationary disc 447 is secured to the shaft 446. Motors 448a and 448bare mounted on the peripheral portions of the stationary disc 447 withangles of 60° and 120° on the left side thereof (in the rotatingdirection of the rotary disc 403) with respect to the line connectingthe container feeding station 405 and the shaft 446. The end of theoutput shaft 449 of the motor 448a (FIG. 19) is provided with a drivinggear 450 which is engaged with the rotating gear 445.

The container feeding station 405 serves, as shown in FIGS. 17 and 18,to hold the container 401 conveyed by the container feeding device 406to the first container conveyer. When the container 401 reaches thecontainer feeding station 405, the arms 444a of the container holder 404are opened to receive the container 401 and the flanged portion 414 ofthe opening of the container is nipped by the three rollers 441, 443 and443.

The first inspecting station 407 is positioned, as shown in FIGS. 17 and18, to a position apart from the container feeding station 405 by anglesof 60° in the direction of rotation of the rotary disc 403. As shown inFIG. 19, an L-shaped sensor supporting rod 471 is located above the mainstructure 472 and to the front end of the supporting rod 471 is attachedan inspection device 476 to which a light projecting fiber 473, a lightreceiving fiber 474 having a guide and a slit member 475 are secured.

The container 401 fed from the container feeding station 405 togetherwith the rotary disc 403 by the angles of 60° in the rotating directionthereof to the first inspecting station 407 is rotated by the motor 448athrough the roller 441, whereby the amount of the heat resistant resinof the opening of the container 401, the verticality, the degree of thetransparency, the height, the bubble amount of the opening portion ofthe container 401 are inspected by the inspecting device 476 and manyother inspecting devices.

The second inspecting station 408 for inspecting the wall thickness ofthe container 401 is positioned, as shown in FIGS. 17 and 18, to aposition apart from the first inspecting station 407 by the angles of60° in the rotating direction of the rotary disc 403.

FIG. 20 shows one example of the second inspecting station 408, whichincludes a plurality of light emitting elements (four light emittingelements 416a, 416b, 416c and 416d in the illustrated example) disposedexternally of the container 401 and directed to the axial directionthereof. The second inspecting station 408 further includes a projector415 for emitting the inspection lights 417a, 417b, 417c and 417d throughthe respective light emitting elements towards the shell of thecontainer 401, a light receiver 418 having a plurality of lightreceiving elements 419a, 419b, 419c and 419d disposed in the axialdirection of the container 401 at locations opposed to the correspondinglight emitting elements 416a, 416b, 416c, and 416d of the projector 415with the predetermined space therebetween, an arithmetic operationdevice 420 for calculating the wall thicknesses of the shell portions ofthe container to be inspected in accordance with the output signals fromthe light receiver 418, and an elevating device 421 for integrallyelevating the light projector 415 and the light receiver 418.

The container 401 conveyed to the second inspecting station by therotation of the rotary disc 403 is rotated by the motor 448b through theroller 441 and, in the second inspecting station, non-destructive andnon-contact type thickness inspections are performed in a short time atmany portions of the container 401 in both the axial and circumferentialdirections by inserting the light receiver 418 into the container 401through the opening thereof.

The container receiving end portion 409 is located at the upstream endof the second container conveyer 411 for conveying the container 401which is judged to be a good product in the first and second inspectingstations 407 and 408. The container receiving end portion 409 ispositioned at a portion apart from the second inspecting station 408 bythe angles of 60° in the rotating direction of the rotary disc 403 asshown in FIGS. 17 and 18.

Only the containers 401 which are conveyed to the container receivingend portion 409 by the rotation of the rotary disc 403 and judged to begood products through the inspections of the first and second inspectionstations 407 and 408 are released from the container holders 404 andthen transferred to the second container conveyer 411.

The first container discharging station 410 is positioned apart from thesecond container conveyer 411 by an angle of 60° in the rotatingdirection of the rotary disc 403. The containers 401 which aredetermined to be faulty products through the inspection of at least oneof the first and second inspecting station 407 and 408 are released fromthe holders 404 and then discharged externally from the inspectingsystem through the first container discharging station.

As described hereinbefore, the container feeding station 405, the firstinspecting station 407, the second inspecting station 408, the containerreceiving end portion 409, and the first container discharging station410 are all arranged around the circumference of the rotary disc 403apart from each other in this order by the angles of 60° in thedirection of rotation thereof, so that the holding, inspecting,releasing and discharging of the containers 401 can be effectivelyperformed through the intermittent rotation of the rotary disc throughangles of 60° , respectively.

The container holder 404f, in FIG. 18, is positioned at the intermediateportion between the container feeding station 405 and the containerdischarging station 410 for the next container holding operation at thecontainer feeding station 405.

The second container conveyer 411 is adapted to convey the container 401fed from the first container conveyer 402 and received by the containerreceiving end portions 409 and the conveyer 411 may be constructed by aconveyer belt means, for example, of known type. The third containerinspecting station 412 is arranged along the conveying passage of thesecond container conveyer 411 as shown in FIG. 17.

The third inspecting station 412 performs the inspection of the airtightness of the container 401 two by two each inspecting time, usually,by a known inspecting means.

The containers 401 judged to be faulty products by the third inspectingstation 412 are discharged externally through the second dischargingstation 413.

Accordingly, only the containers 401 which are determined to be goodproducts through the inspections of the first, second and thirdinspecting stations 407, 408 and 412 are conveyed to the next processingstation.

3-2 Effects

According to the inspecting system for the containers made of syntheticresin, the following effects will be attained:

In the automatic and continuous container manufacturing line, the wallthickness inspecting process regarding the heat resisting property ofthe container is incorporated in the other inspecting processes, forexample, for inspecting the existence of the heat resistant resin at theopening portion of the container, whereby the inspection of thecontainer regarding the heat resisting property of the container can beextremely effectively performed and the manufacturing efficiency of thecontainers having stable qualities can be improved.

What is claimed is:
 1. An apparatus for inspecting a wall thickness of a container made of synthetic resin, comprising:light projector means for projecting an inspection light for insertion into a container made of a synthetic resin so the an open end of said light projector means projects said inspection light toward a wall of the container, light receiver means arranged outside of the container so as to oppose the open end of the light projector means for receiving the inspection light passing through the wall of the container and converting the received light into an electrical signal, inspection position changing means for changing a container inspecting position, and calculation means for calculating the wall thickness of the container on the basis of the electric signal from the light receiver means, wherein the light receiver means comprises a photoelectric transfer element having cooling means incorporated therein for cooling said photoelectric transfer element; wherein the inspecting position changing means is a rotary means for rotating the container axially and comprises a pair of clamp arms each having a roller follower and a drive roller disposed between said pair of clamp arms; and wherein said calculation means comprises:central control means for providing central control of the apparatus, interface control means for controlling interfacing of data with the light receiver means, drive means for driving a chopper, signal processing means for processing signals of the light receiver means and the chopper, rotary encoder means for encoding a rotary position of the container, and arithmetic operation means for performing arithmetic operations on said data.
 2. An apparatus for inspecting a wall thickness of a container made of synthetic resin according to claim 1, wherein the inspecting position changing means is movable in the axial direction of the container while maintaining a constant corresponding relationship between the light projector means and the light receiver means.
 3. An apparatus for inspecting a wall thickness of a container made of synthetic resin according to claim 1, wherein the inspection light is an infrared ray having a wavelength of 2 to 5 μm.
 4. An apparatus for inspecting a wall thickness of a container made of synthetic resin according to claim 1, wherein the light projector means is independently movable in a vertical direction.
 5. An apparatus for inspecting a wall thickness of a container made of synthetic resin, comprising:light projector means for projecting an inspection light for insertion into a container made of a synthetic resin so that an open end of said light projector means projects said inspection light toward a wall of the container; light receiver means arranged outside of the container so as to oppose the open end of the light projector means for receiving the inspection light passing through the wall of the container and converting the received light into an electrical signal; inspection position changing means for changing a container inspecting position; and calculation means for calculating the wall thickness of the container on the basis of the electric signal from the light receiver means; means the light receiver means comprises a photoelectric transfer element having cooling means incorporated therein for cooling said photoelectric transfer element; and wherein the inspecting position changing means is a rotary means for rotating the container axially and comprises a pair of clamp arms each having a roller follower and a drive roller disposed between said pair of clamp arms. 